We
develop a fast-response and flexible nanocrystal-based humidity
sensor for real-time monitoring of human activity: respiration and
water evaporation on skin. A silicon-nanocrystal film is formed on
a polyimide film by spin-coating the colloidal solution and is used
as a flexible and humidity-sensitive material in a humidity sensor.
The flexible nanocrystal-based humidity sensor shows a high sensitivity;
current through the nanocrystal film changes by 5 orders of magnitude
in the relative humidity range of 8–83%. The response/recovery
time of the sensor is 40 ms. Thanks to the fast response and recovery
time, the sensor can monitor human respiration and water evaporation
on skin in real time. Due to the flexibility and the fast response/recovery
time, the sensor is promising for application in personal health monitoring
as well as environmental monitoring
